Amplified piezoelectric actuators utilize a piezoelectric actuator and a displacement amplifier to generate a mechanical action. The piezoelectric actuator can be in form of a stack, bender or membrane. By applying a voltage to the piezoelectric actuator and removing the voltage from the piezoelectric actuator, the piezoelectric actuator undergoes displacement (e.g., expansion and contraction), the displacement having a force component. However, for most industrial applications typical piezoelectric actuators have very limited displacement with significant force. Therefore, various amplifier design approaches are adopted to amplify the displacement, which consequently reduces the force component. One of the most popular amplifier designs is a lever arm design. With such design, a piezoelectric actuator can be mechanically coupled to a device, such as a valve, thereby enabling the valve to be electrically opened or closed, e.g., by applying a voltage to and removing the voltage from the piezoelectric actuator.
Piezoelectric actuators used for valve applications typically require relatively high voltage to generate useful displacement and force. The voltage typically is on the order of 70 volts and up. Combined with the piezoelectric actuator's capacitive nature, stored energy and risk of spark generation in failure mode have been a concern, particularly in applications in which the environment could be explosive. In order to use piezoelectric actuators in such applications, the actuation voltage typically is lowered and the size of the piezoelectric actuator is reduced to limit the stored energy.
One major drawback of the above approach is that the displacement (also referred to as stroke) and force provided by the piezoelectric actuator become limited. This can result in insufficient displacement of the valve mechanism (resulting in limited flow) and/or reduced force (resulting in leakage at the valve close position).